Electric heaters employing semiconductor heating elements represent a marked improvement over prior resistance-wire type heaters. These new heaters include heating elements which consists of a planar core of semiconductor material formed with a multiplicity of apertures that permit passage of air to draw heat from the core. Opposing faces of the core are coated with electrically conductive coatings that produce a fairly even distribution of current flow in the core when a voltage difference is applied to the coatings. These heaters tend to be more durable than prior resistance-wire type heaters, tend to be more compact for a given heat requirement, and have the additional advantage that very hot air flows can be produced while the temperature of the associated heating element remains below about 200 degrees centigrade, thereby reducing the risk of fire, particularly where there are flammable materials in the heated environment. Such a heater was proposed by me in my Canadian Pat. No. 1,119,579.
Heaters incorporating semiconductor heating elements of the type described above are still relatively novel, and a number of problems have arisen in the construction of such heaters. In particular, a convenient, inexpensive mechanism is required to hold the heating elements. The exact manner in which the heating elements are held tends to be more critical in the new type heaters than in the old resistance-wire type, as the heating elements tend to be smaller, and air flows from an associated fan must consequently be more tightly constrained to achieve the full benefit of employing such heating elements. As well, because of the size and nature of the heating elements, considerable care must be taken to ensure simultaneous electrical and thermal isolation of the heating elements from any associated housing, and proper electrical contact with a supply of line voltage. Moreover, it is desirable to improve the heat transfer efficiency of such a heater, and to provide quieter operation, operation tending to be noisy because of the extent to which air flows are affected by the limited cross-sectional area of the new heating elements.
Accordingly, it is one object of the present invention to provide a heater construction employing semiconductor heating elements of the type described above which results in improved heat transfer and quiet operation.
It is another object of the invention to provide a convenient, inexpensive mechanism for holding and electrically contacting semiconductor heating elements of the type described above.